1. Field of the Invention
This invention relates in general to cyclones and more particularly to cyclones having a vibration system for improving the separation of fine particles from a swirling slurry of materials being classified in the cyclone.
2. Description of the Prior Art
Cyclones are mechanisms used in various industries to separate different sized particles of materials that are fed as a slurry into the inlet of the cyclone. In the mineral processing industries such as for example in the processing of copper, iron ore, lead/zinc, gold, coal and the like, a plurality of large cyclones are typically carried in mounting bases arranged in a cluster over a “tub”. Each of the cyclones are in circuit with grinding mills and a slurry formed of a liquid, often times water, and the mineral to be classified is fed into the inlet of the cyclone. The larger, and therefore heavier materials in the slurry exit through an underflow outlet at the bottom of the cyclone and are returned to the grinding mill for reprocessing and are subsequently returned to the cyclone. The smaller, and therefore lighter materials are carried upwardly in a vortex created within the cyclone and exit through an overflow outlet nozzle at its upper end.
The primary components of a cyclone include an inlet housing having a feed duct, a cylindrical head section, a head section cover plate with a vortex finder located centrally in the cover plate. A downwardly tapering conical housing depends from the head section and an apex cone is located at the lower end of the conical housing with the heavy material underflow outlet being connected to the lower end of the apex cone. The overflow outlet nozzle is coupled to the vortex finder and suitable ducts are provided to carry away the slurry containing the lighter materials. In some cyclones, the internal surfaces of the various components thereof are provided with replaceable liners which help prevent the cyclone components from being destroyed by the highly abrasive nature of the materials being classified therein.
The feed duct of a cyclone, which is often referred to as an involute, receives the slurry at high velocity from the grinding mill and directs it tangentially into the cylindrical inlet head section of the cyclone. As the slurry swirls around in the head section, centrifugal force will keep the slurry adjacent the sidewalls of the cyclone as it moves downwardly under the influence of gravity into the conical housing of the cyclone. Also, centrifugal force will cause the larger particles of the materials being classified to migrate to the outside of the slurry at a relatively rapid rate and the finer particles will migrate at a comparatively slower rate. Therefore, a portion of the finer particles will be carried in the inner portions of the slurry and some will migrate to the outer portion thereof. The larger particles the will move downwardly and will exit the cyclone through the underflow outlet. The lighter materials located in the inner portion of the slurry along with the liquid carrying them will enter the vortex created within the apex cone and will move upwardly through the center of the conical housing into the vortex finder and exit the cyclone through the overflow outlet.
There is not a clear demarcation between the larger and smaller particles of the materials within the swirling slurry and some of the lighter particles are located within the outer portion of the slurry along with the larger particles. An undesirable amount of the lighter particles that are located in the outer portion of the slurry become trapped therein and exit the cyclone along with the larger particles through the underflow outlet of the cyclone. This keeps the operating efficiency of cyclones below an ideal level, which effects the entire system including the grinding mill, the pumps that supply the slurry to the cyclones and the cyclones themselves. The resulting low efficiency of the system effects the time, energy usage, the costs for processing the materials, and of course the longer a system must operate to process a given quantity of material the greater the wear will be on the system components.
To the best of my knowledge, no prior art mechanism or method has been devised to help release the smaller particles which become trapped in the downwardly spiraling slurry within a cyclone. Therefore, a need exists for a new and useful mechanism and method for use in a materials classifying cyclone to reduce the quantity of small particles trapped in the outer portions of the slurry so that they can enter the vortex of the cyclone rather than exiting therefrom along with the larger particles.